add new check to find OSSpinlock usage

[Wizard]

Summary

This check finds the use of methods related to OSSpinlock in Objective-C code, which should be deprecated due to livelock issues.
The following method call will be detected:

• OSSpinlockLock()
• OSSpinlockTry()
• OSSpinlockUnlcok()

[Wizard]

add doc to header file

[hokein]

The implementation looks good, I will let Ben to do the Object-C specific review since he probably knows more about it.

clang-tidy/objc/AvoidSpinlockCheck.cpp

36

nit: clang-tidy message is not a complete message, please follow the rule.

The OSSpinlock is also deprecated on macOS, I think? from https://developer.apple.com/documentation/os/1646466-os_unfair_lock_lock.

[hokein]

clang-tidy/objc/AvoidSpinlockCheck.cpp

36

oops, sorry for my typo: s/is not a complete message/is not a complete sentence.

[Wizard]

fix nit

[benhamilton]

clang-tidy/objc/AvoidSpinlockCheck.cpp

22–24

Why? OSSpinLock() calls should also be avoided in C++.

I think you should remove this.

27

matchesName() uses a regular expression, and is many orders of magnitude slower than hasAnyName(A, B, C).

Can you change to hasAnyName(), please?

clang-tidy/objc/CMakeLists.txt

4

IMHO this is really a check which should apply to products built on Apple SDKs, not for Objective-C.

I don't know if that means we should move this to an apple submodule or if there is a better solution.

You don't have to move it in this review, but let's open up a discussion to figure out where non-ObjC checks should go.

docs/clang-tidy/checks/objc-avoid-spinlock.rst

13

Typo: Unlcok -> Unlock

[Wizard]

address comments

[Wizard]

clang-tidy/objc/CMakeLists.txt

4

Sure. It would be a good time to move them when we have more apple checks like this.

[benhamilton]

clang-tidy/objc/AvoidSpinlockCheck.cpp

32–33

Please fix hokein@'s comment — this should be a full sentence. Try this:

Use os_unfair_lock_lock() or dispatch queue APIs instead of the deprecated OSSpinLock().

clang-tidy/objc/AvoidSpinlockCheck.h

20

Remove "in Objective-C files".

docs/ReleaseNotes.rst

63

Remove "in Objective-C files".

docs/clang-tidy/checks/objc-avoid-spinlock.rst

7

Remove "in Objective-C files".

[Wizard]

fix doc

[benhamilton]

Thanks, looks good. Just one question about the test.

test/clang-tidy/objc-avoid-spinlock.m

5

Not sure why you declared (and defined?) this one but not the others.

Either declare them all (no definition needed) or don't..

[Wizard]

test/clang-tidy/objc-avoid-spinlock.m

5

Oh I added this when I tested the first method since I thought it is needed. But looks like I don't have to. Removed it.

[Wizard]

fix test

[benhamilton]

test/clang-tidy/objc-avoid-spinlock.m

5

It probably raises a compiler warning since the function isn't declared, but that does not cause the test to fail.

[Wizard]

fix conflict

clang-tidy/objc/AvoidSpinlockCheck.h

+//===--- AvoidSpinlockCheck.h - clang-tidy-----------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_OBJC_AVOID_SPINLOCK_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_OBJC_AVOID_SPINLOCK_H
+
+#include "../ClangTidy.h"
+
+namespace clang {
+namespace tidy {
+namespace objc {
+
+/// Finds usages of OSSpinlock in Objective-C files, which is deprecated due to
+/// potential livelock problems.
+///
+/// For the user-facing documentation see:
+/// http://clang.llvm.org/extra/clang-tidy/checks/objc-avoid-spinlock.html
+class AvoidSpinlockCheck : public ClangTidyCheck {
+ public:
+  AvoidSpinlockCheck(StringRef Name, ClangTidyContext *Context)
+      : ClangTidyCheck(Name, Context) {}
+  void registerMatchers(ast_matchers::MatchFinder *Finder) override;
+  void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
+};
+
+}  // namespace objc
+}  // namespace tidy
+}  // namespace clang
+
+#endif  // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_OBJC_AVOID_SPINLOCK_H

clang-tidy/objc/AvoidSpinlockCheck.cpp

+//===--- AvoidSpinlockCheck.cpp - clang-tidy-------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "AvoidSpinlockCheck.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang {
+namespace tidy {
+namespace objc {
+
+void AvoidSpinlockCheck::registerMatchers(MatchFinder *Finder) {
+  // The check only applies to Objective-C.
+  if (!getLangOpts().ObjC1 && !getLangOpts().ObjC2) {
+    return;
+  }
+  Finder->addMatcher(
+      callExpr(
+          callee((functionDecl(matchesName("::OSSpinlock(Lock|Unlock|Try)")))))
+          .bind("spinlock"),
+      this);
+}
+
+void AvoidSpinlockCheck::check(const MatchFinder::MatchResult &Result) {
+  const auto *MatchedExpr = Result.Nodes.getNodeAs<CallExpr>("spinlock");
+  diag(MatchedExpr->getLocStart(),
+       "deprecated usage of OSSpinlock; Please use other locks or dispatch "
+       "queue");
+}
+
+}  // namespace objc
+}  // namespace tidy
+}  // namespace clang

clang-tidy/objc/CMakeLists.txt

 set(LLVM_LINK_COMPONENTS support)
 
 add_clang_library(clangTidyObjCModule
+  AvoidSpinlockCheck.cpp
   ForbiddenSubclassingCheck.cpp
   ObjCTidyModule.cpp
   PropertyDeclarationCheck.cpp
 
   LINK_LIBS
   clangAST
   clangASTMatchers
   clangBasic
   clangLex
   clangTidy
   clangTidyUtils
   )

clang-tidy/objc/ObjCTidyModule.cpp

 //===--- ObjCTidyModule.cpp - clang-tidy --------------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 
 #include "../ClangTidy.h"
 #include "../ClangTidyModule.h"
 #include "../ClangTidyModuleRegistry.h"
+#include "AvoidSpinlockCheck.h"
 #include "ForbiddenSubclassingCheck.h"
 #include "PropertyDeclarationCheck.h"
 
 using namespace clang::ast_matchers;
 
 namespace clang {
 namespace tidy {
 namespace objc {
 
 class ObjCModule : public ClangTidyModule {
 public:
   void addCheckFactories(ClangTidyCheckFactories &CheckFactories) override {
+    CheckFactories.registerCheck<AvoidSpinlockCheck>(
+        "objc-avoid-spinlock");
     CheckFactories.registerCheck<ForbiddenSubclassingCheck>(
         "objc-forbidden-subclassing");
     CheckFactories.registerCheck<PropertyDeclarationCheck>(
         "objc-property-declaration");
   }
 };
 
 // Register the ObjCTidyModule using this statically initialized variable.

docs/ReleaseNotes.rst

 Improvements to clang-rename
 ----------------------------
 
 The improvements are...
 
 Improvements to clang-tidy
 --------------------------
 
+- New `objc-avoid-spinlock
+  <http://clang.llvm.org/extra/clang-tidy/checks/objc-avoid-spinlock.html>`_ check
+
+  Add new check to detect the use of OSSpinlock in Objective-C files.
+
 - New `google-avoid-throwing-objc-exception
   <http://clang.llvm.org/extra/clang-tidy/checks/google-objc-avoid-throwing-exception.html>`_ check
 
   Add new check to detect throwing exceptions in Objective-C code, which should be avoided.
 
 - New `objc-property-declaration
   <http://clang.llvm.org/extra/clang-tidy/checks/objc-property-declaration.html>`_ check
 

docs/clang-tidy/checks/list.rst

.. toctree::
    modernize-use-equals-delete
    modernize-use-noexcept
    modernize-use-nullptr
    modernize-use-override
    modernize-use-transparent-functors
    modernize-use-using
    mpi-buffer-deref
    mpi-type-mismatch
+   objc-avoid-spinlock
    objc-forbidden-subclassing
    objc-property-declaration
    performance-faster-string-find
    performance-for-range-copy
    performance-implicit-conversion-in-loop
    performance-inefficient-string-concatenation
    performance-inefficient-vector-operation
    performance-type-promotion-in-math-fn

docs/clang-tidy/checks/objc-avoid-spinlock.rst

+.. title:: clang-tidy - objc-avoid-spinlock
+
+objc-avoid-spinlock
+===================
+
+Finds usages of OSSpinlock in Objective-C files, which is deprecated due to potential
+livelock problems. 
+
+This check will detect following function invocations:
+
+- `OSSpinlockLock`
+- `OSSpinlockTry`
+- `OSSpinlockUnlcok`
+
+The corresponding information about the problem of OSSpinlock: https://blog.postmates.com/why-spinlocks-are-bad-on-ios-b69fc5221058

test/clang-tidy/objc-avoid-spinlock.m

+// RUN: %check_clang_tidy %s objc-avoid-spinlock %t
+
+typedef int OSSpinLock;
+void OSSpinlockTry(OSSpinLock *__lock) {}
+
+@implementation Foo
+- (void)f {
+    int i = 1;
+    OSSpinlockLock(&i);
+    // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: OSSpinlock is deprecated on iOS. Please use other locks or dispatch queue. [objc-avoid-spinlock]
+    OSSpinlockTry(&i);
+    // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: OSSpinlock is deprecated on iOS. Please use other locks or dispatch queue. [objc-avoid-spinlock]
+    OSSpinlockUnlock(&i);
+    // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: OSSpinlock is deprecated on iOS. Please use other locks or dispatch queue. [objc-avoid-spinlock]
+}
+@end